Method of manufacturing double superphosphate.



STATES ATENT OFFICE.

THOMAS LEOPOLD WILLSON AND MAXIMILIAN MATTHEUS HAFF, OF OTTAWA, ONTARIO, CANADA; SAID HAFF ASSIGNOR TO SAID WILLSON.

METHOD OF MANUFACTURING DOUBLE SUPERPI-IOSPI-IATE.

No Drawing.

To all whom it may concern Be it known that we, THOMAS LEOPOLD WILLSON and MAXIMILIAN MA'rrHnUs HArr, of the city of Ottawa, Province of Ontario, Dominion of Canada, have invented certain new and useful Improvements in Methods of Manufacturing Double superphosphate, of which the following is the specification.

This invention relates to an improved method of manufacturing double superphosphate such'as monocalcium phosphate.

The objects of the invention are to produce a dry product, toreduce the amount of insoluble matter and lessen the quantity of free phosphoric acid in the mixture.

The usual method of manufacturing double superphosphate is to add the commercial quality phosphoric acid to a natural phosphate rock. The phosphoric acid used in this reaction is usually umnufactured by adding sulfuric acid to natural or bone phosphate and is known to be" composed solely of ortho-phosphoric acid. The addition of this produces a product which is naturally moist and which cannot be handled and distributed for fertilizing purposes without further artificial drying treatment. We have discovered that if the ordinary orthophosphoric acid of commerce inthis process be replaced by pyro-phosphoric acid, then a new and naturally dry product may be obtained and the apparent solvent action of the acid is materially increased.

The solution of pyro-phosphoric acid for the process may be produced by boiling ordinary phosphoric acid to a temperature of from 209 to 220 degrees centigrade. It may also be produced directly by heating natural phosphate rock with silicious material in the electric furnace. The phosphoric acid expelled from the furnace will be found to be .of the meta variety, and it may be necessary to boil a solution of it to bring it to the pyro state.

In carrying out the process in practice a solution containing pyro-phosphoric acid however obtained is brought. to a specific gravity of about 1.5 and added to natural phosphate rock, and mixed therewith in suitable proportions to produce double superphosphate in the manner at present carried out with ordinary commercial phosphoric acid.

It will be found that the mixture of natu- Specification of Letters Patent.

ral phosphate with the pyro phosphoric acid will quickly set in a cake like plaster which may readily be broken 'or dislntegrated. This phenomena of setting is believed to be quite new in this rocess as commercially carried out and in icates that the double superphosphate product produced is inherently or naturally dry. This natural dryness which is not lost by exposure, renders the new product very useful as a fertilizer and gives it the important advantage over ordinary double superphosphate that Patented Nov. 18, 1913.

Application filed June 23, 1913. Serial No. 775,436.

it is not necessary to artificially dry it prior to use as a fertilizer It is also found that about 15% more rock than usual may be added without materially increasing the amount of insoluble material in the resultant double superphosphate, apparently due to the greater solvent action of the pyrophosphoric acid. There is a lesser quantity of free P 0 in the resultant mass. Experiments have shown that the amount of free P 0 in the resultant mass prepared as above indicated is about 3% as compared with six to eight per cent. in the double superphosphate of commerce.

The term set employed herein as applied to double superphosphate is used to describe a double superphosphate which in the process of manufacture has been set like plaster, and is therefore naturally dry.

lVhile it has been stated that a solution of pyro-phosphoric acid is used in the process, this term is to be understood to include a solution which only partially consists of pyro-phosphoric acid'and which may contain the ortho or meta varieties as well.

lVhat we claim as our invention is:

1. The herein described method of manufacturing superphosphates which comprises adding pyro-phosphoric acid to natural phosphate rock. i

2. As a new article of manufacture, normally dry double su erphosphate.

3. As a new artic e of manufacture, normally dry and set double superphosphate.

In witness whereof we have hereunto set our hands in the presence of two witnesses.

THOMAS moron) WILLSON. mxmrnnr MATTHEUS HAFF. 

